The project will use the behavior of alveolar macrophages in tissue culture as a model to investigate local macrophage proliferation, differentiation, and activation under normal steady state conditions and in response to inflammatory stimuli. We will purify colony stimulating factor (CSF) from media conditioned by mouse L. cells, hamster BHK cells and rat embryo fibroblasts. We will attempt to examine the binding of CSF to macrophages in terms of its specificity, kinetics and morphology and to examine the influence of CSF on differentiated macrophage functions including phagocytosis, lysosomal enzyme content and neutral protease secretion. To determine whether alveolar macrophage colony forming cells are a specific subset of cells distinguishable from the remainder of the alveolar macrophages, we will study the proliferative behavior of all macrophages by time lapse cinemicrography. We will characterize alveolar macrophage enclosed in diffusion chambers and implanted in the peritoneal cavity of other animals. We will investigae the production of CSF by lungs from normal and endotoxin-treated animals.